Reciprocating pumps are widely used for the transfer of fluids because they have a high pumping efficiency and can be readily connected to an appropriate power source. While many pumps of this type are operated for a reciprocating power source such as an air motor, a great many are also operated from rotary power sources. This last class of reciprocating pumps typically utilizes a conventional crank shaft and connecting rod arrangement to reciprocate a piston, for this is an old and proven power translational device. The piston is either in direct contact with the fluid to be pumped or, as is the case with the preferred embodiment of the present invention, may be isolated from the fluid to be pumped by means of an intermediate diaphragm. In this case, the reciprocating piston moves a hydraulic fluid which forces the diaphragm to reciprocate, and the diaphragm moves the fluid to be pumped through a suitable check valve system. The stroke of the piston in a typical diaphragm pump arrangement can be very short, on the order of one-half inch or less, but the rate of reciprocation may be as high as several thousand strokes per minute. The reciprocating drive mechanism for such pumping requirements in the past have included a wobble plate drive mechanism such as is described in U.S. Pat. No. 3,775,030, issued Nov. 27, 1973, Wanner; a rotating eccentric driving a ball bearing assembly such as described in U.S. Pat. No. 2,678,005, issued May 11, 1954, Messick; or a cam operated rod such as is described in U.S. Pat. No. 2,064,750, issued Dec. 15, 1936, Hurst.